Thermoelectric generator



Feb'. 22, 1927,

N. ADAS THERBQOELECTRIC GENERATOR.

2 Sheets-Sheet 1 Filed %az-ch 31 1925 Inventor* Tathan H. Adams, His Attong.

2 Sheets-Sheet 2 Feb. 22,192?. N' H ADAMS THERMOELECTRIC GENERATOR Filed March si 1925 Fg. 3.

Patented Feb. 22, 1927.-

UNITED ISTATESH mam PATENT OFF! NATHAN H. ADAMS,`F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

THERMOELECTRIC GENERATOR.

Application filed March 31, 1925. Serial No. 19,733.

This invention relates to improvements in thermo-electric generators, and more particularly to an arrangement for heating the v hot junctions of the thermopile's comprsing such generators.

Thermopiles heretofore have been constructed with little or no regard to thermal .efliciency. A large portion of the heat input inevitably was wasted without having been 1 conveyed to the hot junction of the thermopile. Furthermore, the Construction ordinarily was such that even the heat actually conveyed to thehot junction was in large part wastefully conducted away or otherwise !5 dissipated. i

I have provided a thermopile of high theri mal efliciency and as in accordance with the hereinafter described form of my invention an electric source of heat is utilized, this !0 high thermal eiiiciency is of added importance to provide not only an economical de- Vice but also a device in which heater is not operated at an excessively high tem rature ud hence will 'have' a commercia ly long %5 e.

With these objects in view I have provided a Construction and organization in a thermopile which gives high thermal efliciency.

. In carrying my invention into effect I provide two thermopiles, each having a slot or a groove in the junctions to be heated. T hese .junctions I shall hereinafter'designate as hot junctions. The thermopiles are arranged in abutting relation so that the grooves will i form a central cavity. Within this central cavity or *openin I place a heater element which is electrica lv insulated from the ther- `mopiles, and which is of substantially the same dimensione as the op ring so that the I heater will fit snugly therein. i As a means for further confiniug the heat to the hot junction. I provide a heat conserving device comp'ising a hollow alundum cylinder which substantially sm-rounds the hot junctions and heater. The space between the cylinder and the thermopi le may be filled with any well known heat insulatin means such as asbestos wool or the like. ly means of this arrangement a relativcly large heat' receiving surface is obtained; the heat is delivered directly to the hot junctions, and hoat losses are reduced to a minimum.

The novel features which I believe to be characteristieof my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, will best be understood b reference to the followin description tacn in connection with the thllowing drawing in which Fig. shows a perspective vew of one form of therno-electric generator of the type shown in the copending application of Truman S.

Fullcr, Serial No. 3,199, filed January 17,

1925 Fig. 2 shows a perspective view of the preferred embodimnt of my invention; Fig. 3 is a longitudinal central section of the device shown in Fig. 2, the heater being shown partially in elevatio-n; F ig. 4 is an exploded view showing the particular type of thermoelectric units and heater element used in connection with the device disclosed in Fi 2; FO'. 5 is a cross'sectional view of one orm of ieater.

Referring particularl to Figs. 3 and 4; of the drawing I have esignated two oppositely positioned thermopiles as 1 and 2, each thermopile comprising a structure built up of a number of interconnected thermopiles made of dissimilar metale. The alternate sheets of metal forming the thermocouples are. united on their flat surfaces along their edges without bendin or folding to form an integral zigzag str p with the hot junetions in alignment, as set forth in my copdending application Serial #19,732 filed arch 31, 1925. Insulating material is insorted between the unlike members of the thermopile and the whole compressed into a' compact form. V

In order etliciently to heat the hot junctions of each thermopile, and at the same time retard the passage of heat from the hot junctions to the cold junctions, I provide each thermopile with a projecting portion having a head portion '4 in close relation with a heater, and a reduced connecting porton 13. The head portion 4, which includes t e `otrelativel small mass Compared, with the main bo` y portion of the thennopile, and is provided with a groove 5. The two thermoples 1 and 2 are arranged in abutting rela- -tiou to form a central cavity and are separated from each other at their hot junctions by thin flanged electrically isulating material 6,'such as mica.` A heater 7 is placed within the central cavity, the dimenjunctions of the thermopile, is of sions of the cavit and heater being substant-ially equal so t at a very snug fit is obtaned. i v In providing a reduoed connecting portion 3 to retardthe flow of heat between- A with theheat receiving surface and therefore serves to retard the flow of heat to the cold junctions, yet the 'resistance of the pile is not increased beyond a definite amount.

In this manner, 'while a maximum amount of heating surface is obtained the passage of heat toward the cold junctions is retarded without undue increase of the resistance in the pile. In order to further retain the heatabout the hot junctions I may provide acylindrical member 8 of alnndum which is slotted as shown at 9 and 10. The Slots enable the cylinder to slide over the narrow portions 3 of the thermopiles.

With a thermopile of the construction shown in Fig. 4 it is desirable to provide cooling means in connection with the' main body portion of the pile, and I have shown in Figs. 2 .and 3 one arrangement whereby eflicient cooling may be obtained. The particular combination of cooling fins and thermopiles shown in these figures forms the sub ect matter of the copendin application Serial No. 19,685 of Truman Fuller and Nathan'H. Adams, filed March 31, 1925.

The cooling means comprises a plurality of thin U shaped members 11 of aluminum, or

mg means in position.

other suitable metal, within which the 'thermopiles'fit snugl The vertical portions of the U are mad z relatively wide in order to obtain good radiation. Sections of mica or similar insulating material 12 and 13 separate the bottom and outer end of each thermopile from the cooling means and end plates 14 respectively, while similar sheets of insulating material, not shown, separate the sides of the thermopilc from the sidcs of the cooling means.

Each U shaped cooling member is spaccd from an adjacent member by U shape(l aluminum spacing means 15 having relatvely narrow vertical portions. Two I slaped end plates 14 and 16 which may be of brass or a similar material cooperate with spacing blocks 17 and screws 18 and serve to clamp the upper portions of the cooling and spac- Bolts 19 extend through the lower ends of the spacing means 15 and cooling members 11, and serve to clamp them between" end plates 14 and 16.

A` bolt 20 cooperates with spacing blocks 17 and clanps the cooling means against each side of the respective thermopilcs.

The vertical portion of each end plate 14 and 16 s slotted. The slot in member 16 is substantially the width of the thermopile while that in member 14 is narrow as shown at 21 and is provided with enlarged upper and lower openings 22 and 23. A metal plate 24 fits within the upper enlarged opening and is provided with grooves 25 near 'and into contact with the top and bottom members of the respective piles. The conducting' members are insulated from portions of the thermo-elcctric generator, other than f'the top and bottom members' of each thermopil'e. u

When 'the heater 7 is placed between the two unitsof the thermo-generator, as shown in Fig. 3, bolts 32 are then inserted through openings m each of the end plates 14 and 16 and the two units are Secured in position by means of the nuts 33. Springs 34 surround each bolt 32 between end plates 15, and serve to urge the thermal units apart when the' nuts 33 are unscrewed. The terminals of the two thermopiles may be connected in any suitable manner to place the piles in series or in parallel as desired.

The heater 7 comprises a threaded insulating core 41 of soapstone-or the like. The ends of the core are reduced in diameter and provided with nickel or similar inetallic ferrules 35. The heater wire is wound in the groove on the core and over a portion ot' the nickel ferrules as shown in Fig. 5. The terminals of the winding are spot welded to'the ferrules. I have found that, unless several turns of the heater wire are in contact with a rclativcly large conducting surface, the heater wire will burn out at `its point of attachment to the conducting surface. For this reason I have continued the coil winding at each end torover a conparatively 'large portion of the coil will be of substantially uniform diam- In the form of heater as shown in Fig.

I extend one of the leads through the insulating core as shown at 36 and provide one of the ferrules with a lug' 37 carrying an extension 38. The two terminals of the heater wire as thus formed maybe used in connection with a plug which may be attached to any elect'ic light socket.

Like references are used in Figs. 1 and 4 to indicate like parts. In the device shown in Fig. 1, cooling of the cold junctions is efl'ected by providing the main body portion of the individual members of the ple with a comparatively large area rather than by means of cooling fins. 'An insulated heater 39, substantially rectangular in cross sec-` tion, tits snugly within the slots 5 in the hot junctions,-and insulating strips 40 are inserted between the opposed thermopiles. If desired a hee-t conservng cylinder 8 may be employed to surround the hot junctions asin Fig; 4.

While I have shown and described the preferred embodiment of my invention it is clear that many modifications thereof may be made without departing from the scope of my invention as set forth in the appended claims.

e lVhat I claim as new and desire tosecure by Letters Patent of the United States is:

1. A- thermopile comprisin a plurality of thermo-electric couples, the e ements of said couples being arranged' substantially parallel to one another, each of said couples having at one end thereof a recess adapted to receive a heater.

2.- A thermo-electric unit including a main body portion and a projecting portion, said projecting portion having a groove adapted to receive a heater unit.

3. A thermo-electric unit including a main body portion and a projecting portion having a groove, a heater element within said groove, and an electrical insulator between said heater and projecting portion.

4. A theromo-electric unit comprising a main body portion and a head portion having a groove, a heater in said groove and a reduced portion connecting said head and main body portions.

5. A thermopile conprsng a main body portion and a head portion shaped to partially enclose a heater element, and a reduced portion connecting said head and body portions.

6. A thermopile conprising a main body portion of relatively large mass, and a head portion of relatively small. mass, and a reduced portion connecting said head and main body portions, said head portion including a series of alined hot junctons, and

having a heat receiving surface reater than the cross secton of said reduce portion.

7. A thermo-electric unit comprising two oppositely disposed thermopiles, each thermopile comprising a series of flat parallel elements, each element having a main body portion and a projecting portion rovided with a recess and a heater mounte in said recessed portions.

8. A thermo-electric unit comprising two oppositely disposed thermopiles, each thermopile comprising a series of parallel elements, each element having a main body portion and a 'projecting recessed portion, said recessed portions being adapted to cooperate *with a centrally disposed heater element.

9. Incombination, a thermo-electric unit comprising a plurality of substantially flat arallel elements, each element having a re cessed portion at one end thereof, said recessed portions cooperatin to forin a groove at one end of the unit an a second'thermoelectric unit having a groove, said units being arranged with their grooves in abutting -relation to form a central cavity.

10. In combination a thermo-eleetric unit comprising series of flat, substantially parallel elements, said unit having a groove atone end thereof, a second thermo-electric unit 'having a groove at one end and arranged opposite said first unit with the grooves in abutting relation to form a central cavity, and a heater element within said cavity. i

11. A plurality of thermo-electric units comprising a series of flat, substantally parallel elements, each unit including a main body portion and a projecting portion, said projecting portion being provided at one end with a groove, said units being arranged opposite one another with their grooved ends in abutting relation to form a central cavity, and a heater element in said cavity.

12. In combination a thermo-electric unit comprising series of fiat, substantially parallel elements, said unit having a groove, a second thermo-electric unit having a groove, said units being arranged with their grooves in abutting relation to form a central cavity, a heater element in said cavity, the dimensions of the heater element being substantially equal to the dimensione of said cavty.

13. A thermo-electric unit conprising two oppositely disposed thermopiles, each thermopile conprising a main body portion, a. head portion and a reduced portion connecting said head and body portions, a heater disposed between said thernmpiles and-a heat conserving device substantially surrounding said head portions and heater, and provided with oppositely disposed slots adapted to engage said reduced portions.

14. A thermo-electric unit comprising two oppoitely disposed thermopiles, each thermopile comprisng a main body portion,

- a head portion 'and a, reduced portion conmeeting said head and body portions, a heater disposed between said thermopiles, a heat conserving device adapted to slide upon said reduced portions, and to substantially sur round said head portions and heater.` V

v 15. A thermo-electrio unit comprising' a thermopile having a head portion provi ed with a groove; a heater closely fitting within the groove and a reduced portion connected to said head portion.

16. A thermo-electric unitjcomprising a thermopile having-a main body portion and a head portion, said head portion being provided with a groove, an electrically insulated heater`closely fitting within the roove and a reduced portion connecting sai head and body portion.

'end portion,

17. In combination a thermopile provided with a groove and anelectrical heater' wthin said groove, said heater comprising. a core of insulatng material having a reduced a metallic ferrule on said reduced portion `and a winding on said core and on a portion of said feri-ule.

18. In combination a thermople provided with a grooveand an electrical heater closely fitting within said groove, said heater comprising a core of insulating material having reduced end portionsymetallioferrules on said end 'portions, a winding on said core and ferrules,- the turns of' said winding being of substantially uniform dii ameter throughout the entire extent of said wndng. 4

In witness whereof, I have hereunto set my hand this 30th day of March; 1925.

' NATHAN H. ADAMS. 

